The present invention relates to lifting liquid from boreholes.
Conventional devices for lifting oil from boreholes comprise a pump which is located downhole in the vicinity of a production formation, which may be a considerable distance below the ground surface, and which is connected by a string of sucker rods to a polish rod which extends through the well head and which is coupled via a walking beam to a rotary motor, or to a reciprocating fluid motor which reciprocates the polish rod and thereby the string of sucker rods and the piston of the downhole pump.
A major problem associated with this type of device is the wear to which the polish rod and the string of sucker rods are subjected. An additional major problem associated with strings of sucker rods is the fact that the movement of the sucker rods often wears holes in the walls of well tubing and casing. The polish rod has to suport the weight of the string and it, and the string, are subjected to continual acceleration and deceleration thereby causing considerable stresses in the string. Failure of the sucker rod string can lead to the loss of expensive downhole equipment and the expenditure of considerable non-productive time while downhole equipment is retrieved and replaced. Still another problem associated with strings of sucker rods is the large amount of energy that must be utilized to operate the string in a reciprocating manner.
It is an object of this invention to avoid the disadvantages inherent in the prior art designs.
It is a further object of the invention to provide a novel and improved device and method for lifting production fluids from boreholes.
It is yet a further object to provide a device which is capable of lifting heavy (low gravity) oil from boreholes.
It is a yet further object to provide a device which requires less energy to power it than prior art devices for pumping oil from oil bearing formations.